Pluripotent stem cells such as human embryonic stem cells (hESCs) have the ability to differentiate into any of the three germ layers, giving rise to any adult cell type in the human body. This unique property provides a potential for developing new treatments for a number of serious cell degenerative diseases, such as diabetes, spinal cord injury, heart diseases and the like. For example, unlike organs such as the skin or liver, the heart is not capable of regenerate sufficient cardiomyocytes to undergo extensive repair. Therefore cardiac repair may benefit from cardiomyocytes, which can be differentiated from hESCs or other pluripotent stem cells, being transplanted into the heart.
However there remain obstacles in the development of such hESC-based treatments. Such obstacles include obtaining and maintaining adequate numbers of undifferentiated hESCs in tissue culture and controlling their differentiation in order to produce specific cell types. Stem cell cultures, such as hES cell cultures are typically seeded with a small number of cells from a cell bank or stock and then amplified in the undifferentiated state until differentiation is desired for a given therapeutic application. To accomplish this, the hESC or their differentiated cells are currently cultured in the presence of surfaces or media containing animal-derived components, such as feeder layers, fetal bovine serum, or MATRIGEL. These animal-derived additions to the culture environment expose the cells to potentially harmful viruses or other infectious agents which could be transferred to patients or compromise general culture and maintenance of the hESCs. In addition, such biological products are vulnerable to batch variation, immune response and limited shelf-life.
Some steps have been taken to culture hESCs either in media or on surfaces that are free of animal-derived components. However, the response of hESCs or their differentiated derivatives is difficult to predict as components of the surface or culture medium change. Yet some advances have been made. For example, hESC-derived cardiomyocytes have been cultured in defined serum-free medium. While such culture systems are not completely xeno-free culture systems when the matrices employed contain animal-derived components, such as gelatin and MATRIGEL, they do provide a step toward the eventual clinical application of hESC-derived cardiomyocytes. By way of further example, some synthetic surfaces have been identified that can support differentiation of human epithelial stem cells into epithelial cells. However, the systems employed relied on serum medium for the cell culture, which still potentially causes problem as described before for all biological animal derived components. To date, a completely animal free system employing a chemically defined medium and a synthetic surface has not yet been identified for culturing stem cells or cells derived from stem cells.